Enhanced exhaust flow control feature

ABSTRACT

A valve for use in a pneumatic fluid system, such as an air brake system, is disclosed. The valve provides for fast release of pneumatic fluid from the delivery cavity through the exhaust port upon cessation of flow from the pneumatic fluid reservoir through the supply cavity. The valve includes a flow diverter that restricts fluid flow from the delivery cavity to the supply cavity when pneumatic fluid pressure in the supply cavity is less than that in the delivery cavity with minimal restriction of flow from the supply cavity to the delivery cavity when pressure in the supply cavity is greater than in the delivery cavity.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Provisional Application60/431,305, filed Dec. 6, 2002, entitled Enhanced Exhaust Flow ControlFeature, the entire disclosure of which is hereby incorporated byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT

[0002] This invention was not made by an agency of the United StatesGovernment nor under contract with an agency of the United StatesGovernment.

BACKGROUND OF THE INVENTION

[0003] The present invention relates to a valve for quick release ofpneumatic pressure in a pneumatic fluid system. It finds particularapplication with air brakes used in conjunction with heavy or commercialvehicles and will be described with particular reference thereto. Theinvention may be used in other applications without departing from thespirit and scope of the invention.

[0004] Some air brake valves used in the industry today (e.g., inEurope) do not meet release timing requirements of Federal Motor VehicleSafety Standard (FMVSS) 121, Air Brake Systems. The release timingrequirements relate to how quickly the brakes release after the brakepedal is allowed to return to its normal position. In order to use thesevalves in the worldwide market, the release timing must be improved tomeet the requirements of this market. As shown in FIG. 1, current brakesystem valves utilize a fixed inlet orifice 1 to generate a pressuredifferential across an exhaust diaphragm 2 to enhance the releasetiming.

[0005] When the actuator 3 for the brake valve is released (e.g., footlifted from a brake pedal), the air flows from the brake chamber 4 tothe actuator 3 through a fixed inlet orifice 1. While the fixed inletorifice does provide some pressure differential across the exhaustdiaphragm, relatively little air, less than 50%, actually is exhaustedthrough the exhaust port, and only slight improvements are realized forthe release timing. Moreover, this method restricts the inlet capacityof the valve. Furthermore, this method does not sufficiently improve therelease timing to meet the FMVSS 121 requirements.

[0006] Patent disclosure DE3938101A1 discusses reducing the vent time ofa pressure control valve for improved release timing. In this disclosurea “reflux” valve is placed directly in the inlet flow path, thusrestricting the inlet flow. Inclusion of a reflux valve that restrictsinlet flow doesn't, however, provide both apply and release timingsufficient to meet, for example the requirements of FMVSS 121. Applytiming relates to how quickly the brakes are applied after pressing thebrake pedal. The enhancement for the release timing in disclosureDE3938101A1 degrades the performance of the valve for the apply timing.With the current sizing requirements of the antilock brake system (ABS)valve, it is not capable to meet both apply and release timing of FMVSS121 using the “reflux” valve design.

[0007] The present invention provides a new and improved apparatus andmethod which addresses the above-referenced problems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the accompanying drawings which are incorporated in andconstitute a part of the specification, embodiments of the invention areillustrated, which, together with a general description of the inventiongiven above, and the detailed description given below, serve toexemplify the embodiments of this invention.

[0009]FIG. 1 illustrates a prior art valve;

[0010]FIG. 2 illustrates a flow diverter as positioned during a brakeapplication in accordance with one embodiment of the present invention;and

[0011]FIG. 3 illustrates a flow diverter as positioned during a brakerelease in accordance with one embodiment of the present invention;

[0012]FIG. 4 illustrates a perspective view of the flow diverter inaccordance with one embodiment of the present invention; and

[0013]FIG. 5 illustrates a graph showing test data.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENT

[0014] In order to provide decreased release timing, such as to meet theFMVSS 121 release timing requirements, the delivery air of the air brakesystem valve is diverted to the exhaust port in order to limit theamount of air returning through the inlet port of the valve. In thismanner, the release timing is improved without significantly increasingthe apply timing. The feature described below meets the required releasetiming of FMVSS 121 without significantly restricting the inlet capacityof the valve (see FIGS. 2 and 3) such that the required apply timing ofFMVSS 121 is met. The invention is not limited to features requiringcompliance with FMVSS 121 release and apply timing requirements, but isdiscussed below in relation to features that will meet theserequirements.

[0015] As used herein, “apply timing” means the time from the firstmovement of the brake valve actuator (brake pedal) for the brake chamberto reach 60 psi with an initial service reservoir pressure of 100 psi.As used herein, “release timing” means the time from initial brake pedalmovement (release) for a set of brake chambers initially at 95 psi toreach 5 psi. Unless otherwise specified, use of the term “or” herein isthe inclusive, and not the exclusive, use. See BRYAN A. GARNER, ADICTIONARY OF MODERN LEGAL USAGE 624 (2d Ed. 1995).

[0016] The release timing of a brake valve correlates to how quickly thepressure of the pneumatic fluid therein, often air, is released from thebrake chamber 4 (see FIG. 1). The more quickly the pneumatic fluidpressure applied to the brake chamber 4 is released, the more quicklythe brake will release. The present invention provides for a restrictionin the fluid flow from the brake chamber 4 to more quickly begin fluidcommunication with an exhaust port and to redirect more of the fluid tothe exhaust port after the actuator 3 is released. This creates apressure differential across the exhaust diaphragm 2 to unseat theexhaust diaphragm 2 and exhaust fluid. The greater the pressuredifferential, the more quickly the exhaust diaphragm 2 is unseated andthe greater is the quantity and speed of the fluid exhausted. Unlikeconventional valves that have some restriction, however, the presentinvention provides a restriction that does not significantly reduce theincoming fluid flow upon application of the actuator 3 to engage thebrake. Therefore, there is minimal reduction of the apply timing due tothe restriction.

[0017] Generally, the restriction device, herein called a flow diverter,has at least two positions-a first or open position when the pneumaticfluid flows to actuate the brake and a second or closed position whenthe brake is released. When in the first position, the flow diverterdoes not significantly restrict fluid flow to actuate the brake. When inthe second position, the flow diverter diverts fluid flow to the exhaustby restricting the flow back in the direction of the actuator 3. Theflow diverter may divert all or a portion of the fluid to the exhaust.Thus, the flow diverter does not significantly reduce the apply timing,as does a conventional fixed inlet orifice 1.

[0018]FIG. 2 illustrates a flow diverter 20 as positioned during a brakeapplication, in accordance with one embodiment of the present invention.FIG. 3 illustrates the flow diverter 20 as positioned during a brakerelease operation, in accordance with the embodiment illustrated in FIG.2. Air flow paths of the delivery air during brake application andrelease are shown by arrows in FIGS. 2 and 3, respectively. Flowdiverter 20 moves freely within a bore 22 according to relative airpressures in a supply (inlet) cavity 24 and a delivery cavity 26.

[0019] As shown in FIG. 2, air from a service reservoir (not shown)enters the supply (inlet) cavity 24 via an inlet/outlet port 30 when abrake valve 32 is actuated via, for example, a foot pedal 34. The aircreates pressure in the supply cavity 24 and passes to a control side 36of an exhaust diaphragm 40. The pressure created by the air at thecontrol side 36 creates a stronger force on the exhaust diaphragm 40than the pressure on the other side of the exhaust diaphragm 40 andurges the exhaust diaphragm 40 to seat against a housing wall 42 at apoint 44. Typically, the exhaust diaphragm 40 will be biased to seatagainst the housing wall 42 at point 44. A portion of the other side ofthe exhaust diaphragm 40 is exposed to the pressure of delivery cavity26 and a portion is exposed to the pressure of an exhaust port 46. Thepressure of the exhaust port 46 is generally atmospheric pressure. Aswill be discussed in more detail below, the seating of the exhaustdiaphragm 40 at the point 44 creates a seal between the delivery cavity26 and the exhaust port 46. At the same time, the air creating pressurein the supply cavity 24 also passes through a passage 48 between asupply (hold) diaphragm 50 and a housing wall 52.

[0020] After passing through the passage 48, the air passes into thebore 22. A flow diverter 20, which is described in more detail below, ispositioned within the bore 22. The air exits the bore 22 via a passage(not shown) into the delivery cavity 26. Because of the seal createdbetween the delivery cavity 26 and the wall 42 at point 44, the airentering the delivery cavity 26 from the bore 22 does not pass to theexhaust port 46; instead, the air passes from the delivery cavity 26 toa delivery port 56 and then to a brake chamber 60.

[0021] As shown in FIGS. 2 and 4, the flow diverter 20 includes arestrictor portion 100 and a spacer portion 102. In the illustratedembodiment, the restrictor portion 100 is flat; furthermore, the spacerportion includes a plurality (e.g., four) of legs 102 a, 102 b, 102 c,102 d. Additionally, an outer diameter of the restrictor portion 100 issized to be smaller than an inner diameter of the bore 22. In oneembodiment, the outer diameter of the restrictor portion 100 is about0.475 inches while the inner diameter of the bore 22 is about 0.490inches. The flow diverter 20 illustrated in FIGS. 2 and 4 representsonly one embodiment and other embodiments including other designs,shapes, and/or dimensions of the flow diverter 20 relative to the bore22 are contemplated.

[0022] For example, the surface of restrictor portion 100 may be of anyshape suitable for use, including regular or irregular polygons, such asrectangular, pentagonal, hexagonal, octagonal, or dodecahedral polygons.Preferably, the restrictor portion 100 is circular, if the cross-sectionof the bore 22 is circular. The diameter of the restrictor portion 100is dimensioned relative to the diameter of the bore 22 such that therestrictor portion 100 provides sufficient resistance to the flow of airto divert a sufficient amount, preferably at least about 50%, of the airin the delivery cavity 26 to the exhaust port 46. The flow diverter 20also is dimensioned so that there is minimal restriction in the flow ofair from supply cavity 24 to delivery cavity 26. The restriction is suchthat the desired apply timing may still be obtained. Preferably, theflow diverter 20 provides a restriction in the flow in this direction ofno more than about 25%. Therefore, one of skill in the art may determinethe optimum diameter of the restrictor portion 100 without undueexperimentation.

[0023] Moreover, while the spacer portion 102 is illustrated with fourlegs 102 a, 102 b, 102 c, 102 d, there may be any number of legs,including three legs, so long as there is sufficient stability to enablethe flow diverter 20 to divert the requisite air to the exhaust port 46without significantly restricting the flow of air from the supply cavity24 to the delivery cavity 26 when the brake valve 32 is actuated. Thenumber of legs may be chosen without departing from the spirit and scopeof the invention.

[0024] The shape of the legs 102 a, 102 b, 102 c, 102 d is illustratedas rectangular prisms, but any suitable shape is contemplated, such asany suitable regular or irregular polygon, and is within the spirit andscope of the invention. The shape of the legs 102 a, 102 b, 102 c, 102dis to be selected such that there is minimal interference with air flowbetween the supply cavity 24 and the delivery cavity 26, while providingsufficient support for the restrictor portion 100. For example, theshape of the legs 102 a, 102 b, 102 c, 102 d may be selected to havetapering or curved portions to reduce the turbulent flow characteristicsof the air and to reduce stress points on the flow diverter 20. In onedesign, the legs 102 a, 102 b, 102 c, 102d have a triangular crosssection. There may also be ribs between the legs or otherwise provided,for example, to provide additional strength for the legs.

[0025] The specific dimensions of the restrictor portion 100 and thespacer portion 102 may be selected based on the circumstances andparameters of each particular application without departing from thespirit and scope of the invention. Suitable dimensions may be determinedwithout undue experimentation based on the measurement of the releasetiming and apply timing of the brake.

[0026] Also, the flow diverter 20 may be a spherical ball or acylindrical slug or other shape dimensioned such that, for example, thepressure of the air in the supply cavity 24 is sufficient to move theball or slug substantially out of the way of the flow of air from thesupply cavity 24 to the delivery cavity 26, but the ball or sluginterposes restriction in the flow of air from the delivery cavity 26 tothe supply cavity 24. Thus, the flow diverter 20 need not have both arestrictor portion 100 and a spacer portion 102, but may be provided asone portion.

[0027] Although the flow diverter 20 has been discussed thus far asrestricting flow of air from the supply cavity 24 to the delivery cavity26, but allowing some flow of air in this direction, the flow diverter20 may also completely restrict any flow of air from the supply cavity24 to the delivery cavity 26. There need not be any leak by or flow ofair back into the supply cavity 24 around or through the flow diverter20. For example, a flapper or check valve may be placed in or near thepassage 48 that is in an open position when air is flowing from thesupply cavity 24 to the delivery cavity 26, but is in a closed positionwhen air is no longer flowing in that direction.

[0028] The material from which the flow diverter 20 is made may be anyconventional material selected, for example, based on cost,availability, weight, or any other parameter without departing from thespirit and scope of the invention. Preferably, the material is plastic,but metals, such as aluminum, are also suitable. The specific materialchosen may affect the restriction of fluid flow because of, for example,weight or surface smoothness, but the appropriate shape and dimensionsfor the chosen material may be determined without undue experimentation.

[0029] As illustrated in FIG. 2, the flow diverter 20 is positioned inthe bore 22 upon a brake application such that the flow diverter 20 doesnot substantially interfere with the flow of air from the supply cavity24 to the delivery cavity 26 via the bore 22. For example, therestrictor portion 100 is above the passage (not shown) from the bore 22to the delivery cavity 26. The legs 102 a, 102 b, 102 c, 102 d aredesigned such that they do not substantially interfere with the flow ofair from the bore 22 to the delivery cavity 26 upon brake application.

[0030] As shown in FIG. 3, when the brake valve 32 is no longer actuated(e.g., when the brake valve or foot pedal is released), air begins toflow from the control side 36 of the exhaust diaphragm 40 into thesupply cavity 24. Air in the supply cavity 24 is exhausted via theinlet/outlet port 30, thereby causing a pressure drop in the supplycavity 24. Once the pressure in the supply cavity 24 drops, air beginsto flow from the delivery cavity 26 to the supply cavity 24 via the bore22. The flow diverter 20 is then positioned as shown in FIG. 3. Therestrictor portion 100 reduces the amount of air that flows from thedelivery cavity 26 to the supply cavity 24 via the bore 22 and passage48.

[0031] Because a restricted amount of air is permitted to escape fromthe delivery cavity 26 via the bore 22 and, furthermore, because of thereduced pressure at the control side 36 of the exhaust diaphragm 40, thepressure of air in the delivery cavity 26 urges the exhaust diaphragm 40to become unseated from the wall 42 at the point 44. Consequently, airpasses from the delivery cavity 26 to the exhaust port 46 via a channel62 defined between the exhaust diaphragm 40 and wall 42. Morespecifically, the higher pressure in the delivery cavity 26 unseats theexhaust diaphragm 40, directing the major portion of the delivery airflow out the exhaust port 46. The combination of low pressure on thecontrol side 36 of the exhaust diaphragm 40 and high pressure on theseat side speeds the opening of the exhaust valve and the release timingof the valve.

[0032] As shown in FIGS. 2 and 3, the flow diverter 20 allowsminimally-restricted inlet flow during brake application and meters backflow during brake release. The metering of back flow quickly induces adifferential pressure across the exhaust diaphragm triggering theopening of the exhaust seat. This unseating results in the improvedrelease timing that meets the FMVSS 121 timing requirements.

[0033] The flow diverter 20 is a flow-activated device having twopositions of operation. During a brake application the flow diverter ismoved by the application air to its minimally restricted open position.This allows the ABS valve to meet the FMVSS 121 apply timingrequirement. During the brake application release, the flow of deliveredair carries the flow diverter 20 to its metering position (see FIG. 3).At this position the flow diverter 20 diverts the majority of the air inthe delivery cavity to the exhaust port 46 and restricts the amount ofair returning to the inlet/outlet 30 of the valve 32 through theclearance between its outside diameter and the housing bore's insidediameter.

[0034] A valve available from Knorr Bremse with a part number of BR9164was fitted with a flow restrictor 20 having three legs withsubstantially triangular cross sections. In this embodiment, the innerdiameter of the bore 22 was about 0.490 inches and the outer diameter ofthe restrictor portion 100 was about 0.481 inches. FIG. 5 illustrates agraph 200 of test data showing a reduction in the amount of time forreleasing pressure in the delivery cavity 26 (see FIGS. 2 and 3) from 95psi to 5 psi. A line 202 shows that, for these dimensions, it took about0.564 seconds to release the pressure without the flow diverteraccording to the present invention. Furthermore, a line 204 shows that,for the same embodiment, it took about 0.267 seconds to release thepressure with the flow diverter according to the present invention. Thereduction in flow area for the air passing from the supply cavity 24 tothe delivery cavity 26 imposed by the flow diverter 20 for threedifferent tests was about 23.3%, about 23.8%, and about 23.9%, with anaverage of about 23.7%, or less than 25%.

[0035] While the present invention has been illustrated by thedescription of embodiments thereof, and while the embodiments have beendescribed in considerable detail, it is not the intention of theapplicants to restrict or in any way limit the scope of the appendedclaims to such detail. Additional advantages and modifications willreadily appear to those skilled in the art. Therefore, the invention, inits broader aspects, is not limited to the specific details, therepresentative apparatus, and illustrative examples shown and described.Accordingly, departures may be made from such details without departingfrom the spirit or scope of the applicants' general inventive concept.

We claim:
 1. A valve for use in a pneumatic fluid system comprising: a.a supply cavity for supplying pneumatic fluid; b. a delivery cavity; c.an exhaust port; and d. a flow diverter disposed between the supplycavity and the delivery cavity; wherein the flow diverter is in an openposition when the fluid is communicated from the supply cavity to thedelivery cavity and is in a closed position when the fluid iscommunicated from the delivery cavity to the supply cavity restrictingpneumatic fluid flow such that the majority of pneumatic fluid in thedelivery cavity is communicated to the exhaust port.
 2. The valve ofclaim 1, wherein the flow diverter does not significantly restrict flowof the pneumatic fluid from the supply cavity to the delivery cavity. 3.The valve of claim 2, wherein the flow diverter reduces the flow area byno more than about 25%.
 4. The valve of claim 1, wherein the pneumaticfluid is air.
 5. The valve of claim 1, wherein the pneumatic fluidsystem comprises a vehicle air brake system.
 6. The valve of claim 1,further comprising: a. a housing wall disposed between the deliverycavity and the exhaust port; and b. an exhaust diaphragm capable ofseating against the housing wall.
 7. The valve of claim 6, wherein whenthe pneumatic fluid is at a higher pressure in the delivery cavity thanin the supply cavity, the flow diverter restricts flow of the pneumaticfluid from the delivery cavity to the supply cavity and the diaphragm isunseated from the housing wall, enabling communication of the pneumaticfluid from the delivery cavity to the exhaust port.
 8. A valve for usein a pneumatic fluid system, comprising: a. a supply cavity forsupplying pneumatic fluid; b. a delivery cavity in fluid communicationwith the supply cavity; c. an exhaust port in fluid communication withthe delivery cavity; d. a housing wall disposed between the deliverycavity and the exhaust port; e. an exhaust diaphragm capable of seatingagainst the housing wall between the delivery cavity and the exhaustport; and f. a flow diverter disposed between the supply cavity and thedelivery cavity; wherein the flow diverter allows the pneumatic fluid tobe communicated to the delivery cavity from the supply cavity withminimal restriction by the flow diverter, and wherein when the pneumaticfluid is at a higher pressure in the delivery cavity than in the supplycavity, the flow diverter restricts flow of the pneumatic fluid from thedelivery cavity to the supply cavity, and the diaphragm is unseated fromthe housing wall, enabling communication of the pneumatic fluid from thedelivery cavity to the exhaust port.
 9. A valve for use in a pneumaticfluid system, comprising: a. a supply cavity for supplying pneumaticfluid; b. a delivery cavity in fluid communication with the supplycavity; c. an exhaust port in fluid communication with the deliverycavity; d. means for restricting the flow of pneumatic fluid from thedelivery cavity to the supply cavity with minimal restriction of theflow of pneumatic fluid from the supply cavity to the delivery cavity;and e. means for directing the flow of the majority of the pneumaticfluid in the delivery cavity from the delivery cavity to the exhaustport when pressure of the pneumatic fluid in the delivery cavity exceedspressure of the pneumatic fluid in the supply cavity.
 10. The valve ofclaim 9, wherein the means for restricting the flow of pneumatic fluidcomprises a flow diverter between the supply cavity and the deliverycavity.
 11. The valve of claim 9, wherein the means for restricting theflow of pneumatic fluid reduces the flow area for flow of pneumaticfluid from the supply cavity to the delivery cavity by no more thanabout 25%.
 12. The valve of claim 9, wherein means for directing theflow of the majority of the pneumatic fluid comprises an exhaustdiaphragm capable of seating against and unseating from a housing suchthat when pressure of the pneumatic fluid in the delivery cavity exceedspressure of the pneumatic fluid in the supply cavity, the exhaustdiaphragm unseats from the housing, providing a flow path for thepneumatic fluid between the delivery cavity and the exhaust port.
 13. Aquick release valve for use in a vehicle air brake system, comprising:a. a supply cavity; b. a delivery cavity; c. an exhaust port; and d. aflow diverter that has first and second positions; wherein the supplycavity is in fluid communication with the delivery cavity when the flowdiverter is in the first position and the delivery cavity is in fluidcommunication with the exhaust port when the flow diverter is in thesecond position.
 14. A flow diverter for use in a valve in a pneumaticfluid system, comprising: a. a restrictor portion; and b. a spacingportion having at least one leg; c. wherein the flow diverter isconfigured for placement in a bore between a supply cavity in fluidcommunication with a delivery cavity such that the flow diverterminimally restricts flow of pneumatic fluid when the fluid is beingcommunicated to the delivery cavity from the supply cavity, but willsignificantly restrict flow of the pneumatic fluid from the deliverycavity to the supply cavity.
 15. A method of rapidly exhausting air,with minimal restriction of air inlet flow, from an air brake valvehaving a supply cavity, a delivery cavity, an exhaust port, a housing,and an exhaust diaphragm seated against the housing, comprising: a.restricting communication of the air from the delivery cavity to thesupply cavity when pressure of the air in the delivery cavity is greaterthan pressure of the air in the supply cavity with minimal restrictionof communication of the air from the supply cavity to the deliverycavity when pressure of the air in the supply cavity is greater thanpressure of the air in the delivery cavity; b. unseating the exhaustdiaphragm from the housing when pressure of the air in the deliverycavity is greater than pressure of the air in the supply cavity; and c.causing communication of the air from the delivery cavity to the exhaustport upon unseating the diaphragm from the housing.
 16. The method ofclaim 15, wherein restricting communication of air is accomplished by aflow diverter that is in an open position when pressure of the air inthe supply cavity is equal or greater than pressure of the air in thedelivery cavity and in a closed position when pressure of the air in thedelivery cavity is greater than pressure of the air in the supplycavity.